Piezoelectric drive systems exist in a variety of shapes and configurations. Piezoelectric drive systems employ a piezoelectric element to generate mechanical vibrations in a vibratory element to incrementally move a driven element. Often, the vibratory element comprises a mechanical resonator to amplify and direct the mechanical vibrations. The vibratory element is typically in frictional contact with the driven element at a selected contacting portion of the vibratory element and the vibrations are selected to incrementally move the driven element in a predetermined direction by the vibrations of the selected contacting portion. Typical frequencies of operation can range from a few Hertz to hundreds of Kilohertz. Driven elements can be pushrods, wheels, cams, etc. One type of piezoelectric drive in various drive configurations is, for example, disclosed in U.S. Pat. No. 6,664,714.
Prior art piezoelectric drive systems do not take into account that a first driven element that is moved by vibrations of a selected contacting portion on a vibratory element can transmit the vibrations from the vibratory element to further structures and also to further driven elements that are in frictional contact with that first driven element so that these transmitted vibrations may move additional driven elements by vibrating further contacting portions. In doing so, one vibratory element can move a first driven element by way of piezoelectric vibrations, and the same vibratory element can independently move a second driven element also by way of piezoelectric vibrations. The resulting motions of the first and second driven elements differ from those that would be obtained through simple mechanical gearing between the first and second driven elements. One of the advantages of such a vibratory multistage, preferably piezoelectric, drive system over prior art is that multiple motions of multiple driven elements may independently be generated using one vibratory element, which may lead to more compact piezoelectric drive systems that comprise fewer parts and are cheaper to produce than prior art piezoelectric drive systems for moving multiple driven elements.